From: Huang Ying <ying.hu...@intel.com>
With this patch, a THP (Transparent Huge Page) can be added/deleted
to/from the swap cache as a set of (HPAGE_PMD_NR) sub-pages.
This will be used for the THP (Transparent Huge Page) swap support.
Where one THP may be added/delted to/from the swap cache. This will
batch the swap cache operations to reduce the lock acquire/release times
for the THP swap too.
Cc: Hugh Dickins <hu...@google.com>
Cc: Shaohua Li <s...@kernel.org>
Cc: Minchan Kim <minc...@kernel.org>
Cc: Rik van Riel <r...@redhat.com>
Cc: Andrea Arcangeli <aarca...@redhat.com>
Cc: Kirill A. Shutemov <kirill.shute...@linux.intel.com>
Signed-off-by: "Huang, Ying" <ying.hu...@intel.com>
---
include/linux/page-flags.h | 5 ++--
mm/swap_state.c | 64 ++++++++++++++++++++++++++++++----------------
2 files changed, 45 insertions(+), 24 deletions(-)
diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index 6b5818d6de32..f4acd6c4f808 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -326,11 +326,12 @@ PAGEFLAG_FALSE(HighMem)
#ifdef CONFIG_SWAP
static __always_inline int PageSwapCache(struct page *page)
{
+ page = compound_head(page);
return PageSwapBacked(page) && test_bit(PG_swapcache, &page->flags);
}
-SETPAGEFLAG(SwapCache, swapcache, PF_NO_COMPOUND)
-CLEARPAGEFLAG(SwapCache, swapcache, PF_NO_COMPOUND)
+SETPAGEFLAG(SwapCache, swapcache, PF_NO_TAIL)
+CLEARPAGEFLAG(SwapCache, swapcache, PF_NO_TAIL)
#else
PAGEFLAG_FALSE(SwapCache)
#endif
diff --git a/mm/swap_state.c b/mm/swap_state.c
index 199a07efc44d..504f67d73f67 100644
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -38,6 +38,7 @@ struct address_space *swapper_spaces[MAX_SWAPFILES];
static unsigned int nr_swapper_spaces[MAX_SWAPFILES];
#define INC_CACHE_INFO(x) do { swap_cache_info.x++; } while (0)
+#define ADD_CACHE_INFO(x, nr) do { swap_cache_info.x += (nr); } while (0)
static struct {
unsigned long add_total;
@@ -90,39 +91,52 @@ void show_swap_cache_info(void)
*/
int __add_to_swap_cache(struct page *page, swp_entry_t entry)
{
- int error;
+ int error, i, nr = hpage_nr_pages(page);
struct address_space *address_space;
+ struct page *cur_page;
+ swp_entry_t cur_entry;
VM_BUG_ON_PAGE(!PageLocked(page), page);
VM_BUG_ON_PAGE(PageSwapCache(page), page);
VM_BUG_ON_PAGE(!PageSwapBacked(page), page);
- get_page(page);
+ page_ref_add(page, nr);
SetPageSwapCache(page);
- set_page_private(page, entry.val);
address_space = swap_address_space(entry);
+ cur_page = page;
+ cur_entry.val = entry.val;
spin_lock_irq(&address_space->tree_lock);
- error = radix_tree_insert(&address_space->page_tree,
- swp_offset(entry), page);
- if (likely(!error)) {
- address_space->nrpages++;
- __inc_node_page_state(page, NR_FILE_PAGES);
- INC_CACHE_INFO(add_total);
+ for (i = 0; i < nr; i++, cur_page++, cur_entry.val++) {
+ set_page_private(cur_page, cur_entry.val);
+ error = radix_tree_insert(&address_space->page_tree,
+ swp_offset(cur_entry), cur_page);
+ if (unlikely(error))
+ break;
}
- spin_unlock_irq(&address_space->tree_lock);
-
- if (unlikely(error)) {
+ if (likely(!error)) {
+ address_space->nrpages += nr;
+ __mod_node_page_state(page_pgdat(page), NR_FILE_PAGES, nr);
+ ADD_CACHE_INFO(add_total, nr);
+ } else {
/*
* Only the context which have set SWAP_HAS_CACHE flag
* would call add_to_swap_cache().
* So add_to_swap_cache() doesn't returns -EEXIST.
*/
VM_BUG_ON(error == -EEXIST);
- set_page_private(page, 0UL);
+ set_page_private(cur_page, 0UL);
+ while (i--) {
+ cur_page--;
+ cur_entry.val--;
+ radix_tree_delete(&address_space->page_tree,
+ swp_offset(cur_entry));
+ set_page_private(cur_page, 0UL);
+ }
ClearPageSwapCache(page);
- put_page(page);
+ page_ref_sub(page, nr);
}
+ spin_unlock_irq(&address_space->tree_lock);
return error;
}
@@ -132,7 +146,7 @@ int add_to_swap_cache(struct page *page, swp_entry_t entry,
gfp_t gfp_mask)
{
int error;
- error = radix_tree_maybe_preload(gfp_mask);
+ error = radix_tree_maybe_preload_order(gfp_mask, compound_order(page));
if (!error) {
error = __add_to_swap_cache(page, entry);
radix_tree_preload_end();
@@ -148,6 +162,7 @@ void __delete_from_swap_cache(struct page *page)
{
swp_entry_t entry;
struct address_space *address_space;
+ int i, nr = hpage_nr_pages(page);
VM_BUG_ON_PAGE(!PageLocked(page), page);
VM_BUG_ON_PAGE(!PageSwapCache(page), page);
@@ -155,12 +170,17 @@ void __delete_from_swap_cache(struct page *page)
entry.val = page_private(page);
address_space = swap_address_space(entry);
- radix_tree_delete(&address_space->page_tree, swp_offset(entry));
- set_page_private(page, 0);
+ for (i = 0; i < nr; i++, entry.val++) {
+ struct page *cur_page = page + i;
+
+ radix_tree_delete(&address_space->page_tree,
+ swp_offset(entry));
+ set_page_private(cur_page, 0);
+ }
ClearPageSwapCache(page);
- address_space->nrpages--;
- __dec_node_page_state(page, NR_FILE_PAGES);
- INC_CACHE_INFO(del_total);
+ address_space->nrpages -= nr;
+ __mod_node_page_state(page_pgdat(page), NR_FILE_PAGES, -nr);
+ ADD_CACHE_INFO(del_total, nr);
}
/**
@@ -237,8 +257,8 @@ void delete_from_swap_cache(struct page *page)
__delete_from_swap_cache(page);
spin_unlock_irq(&address_space->tree_lock);
- swapcache_free(entry);
- put_page(page);
+ __swapcache_free(entry, PageTransHuge(page));
+ page_ref_sub(page, hpage_nr_pages(page));
}
/*
--
2.11.0
